Bubble tray construction



Sept. 1, 1936. G w W TT 2,052,994

BUBBLE TRAY CONSTRUCT ION Filed June 29, 1933 T Z g5,

INVENTOR geoz ge N Watts mm ATTORNEY I Fatented. Sept. E, E936 Oil Company, Chicago, Ill., a corporation oii diana Application June 2a, 1933, Serial No. 678,244

bubble towers and more particularly to certain structural features and arrangement of parts having to do with the transposition of the fluid 5 from one tray level to another;

It has become substantially uniform practice to construct bubble towers of a vertical series of bubble trays and to provide downcomers for conducting the fluid from one tray level to the next lower level. One of the difliculties encountered in bubble towers of this type is the condensation of the vapors in the downcomers between the tray levels brought about by the introduction of the vapors into the downcomer through the formation of a vortex in the fluid stream at the head of the downcomer.

\ Another disadvantage attributable to the present fluid conduction arrangement of the bubble tower is the partial choking of the outlet or lower end of the downcomer by the accumulation of tarry or immobile constituents of the processing fluids upon the adjacent portions of the tray wherein a pool of the fluid is maintained to seal the downcomer outlet. At times as during the shut down of the tower the accumulation and further congealing of this heavy substance may completely choke the downcomer outlet opening, thus necessitating disassembly of the units and manual removal of. the obstruction with consequent waste of time and operating expense.

My invention has for an object the provision of simple means for preventing the formation of a vortex at the mouth of the downcomer by the elimination of the presence of vapor at the inlet of the downcomer so that premature fractionation may not take place due to the condensation of the vapors within the downcomer and the subsequent delivery of the fluid 'upon a tray of lower level than that tray from which the proper and 40 required fraction is removed. In other words, I

have provided a safeguard as against the withdrawal, for example of a gasoline fraction with the kerosene or next lower fraction.

Another object is to provide bubble tray fluid 4 approach which serves to discourage the accumulation of heavy and relatively immobile substance at a point where the choking of the downcomer may result, thereby eliminating the hazards of blocking the tower. 50 Other objects, the advantages, and uses of the invention, will become apparent after reading the following specification and claims and after consideration of the drawing forming a part of the specification wherein: 65 Fig. 1 is a horizontal sectional view through a 1 w (CLZBl-lle) This application relates to an improvement in bubble tower incorporating features of the invention, baflie plates over the downcomers and bubble caps over the vapor risers being omitted from the drawing for the sake of cleamess.

Fig. 2 is a sectional view substantially along the 5 line IL-II of Fig. 1, and

Fig. 3 is a schematic view illustrating the manner in which premature fractionation may occur in a conventional bubble tower.

With reference to drawing, l represents the 10 cylindrical walls of the bubble tower and 2 a plurality of bubble tray assemblies at spaced distances from one another along the vertical axis of the tower, each establishing its. own fluid level. The tray assemblies include cast trays 3 having a 15 plurality of vertically extending and rectangular wall sections t providing vapor chambers each of which is provided with a bubble cap 5 having depending walls which extend below the fluid level of the tray. The type of bubble tray illuso trated is one wherein the fluid is caused to pass horizontally from one side of the tray to the other through parallel channels 6 formed by the vertical wall sections 4. Dams i and 8 which may be formed integrally with the tray serve to 25 establish a normal fluid level for the tray; The dams 1 and 8 occupy the positions of the cords of a circle and lie in planes perpendicular to the axes of the fluid channels 6.

In the present embodiment I have illustrated a. 30 pair of downcomers 9 for each tray assembly, substantially elliptical in cross section, although downcomers of other contour may be usedwith equal efi'ectiveness, which extend downwardly through a horizontal portion ll of the tray be- 35 yond the dam l. The upper end or inlet l2 of the downcomers may be above the level of the portion l i but located beneath the upper level of the dam I. Fluid passing over the dam 1 from the trays may therefore flow downwardly through the 40 downcomers 9 to the next lower tray.

A horizontal baflle l3 having a depending skirt is provided for each of the downcomers 9 and is of a size and shape to overhang the outlets 12 ofthe downcomers and to lie beneath the normal level of fluid on the tray but sufliciently above the inlet as to permit of the uninterrupted flow of. fluid therethrough. The baffles 13 may be supported upon rods 14 fixed to horizontal channels i5 as shown in Fig. 2. I have thus efiectively guarded against premature fractionation by the elimination of the possibility of the condensation and absorption of the vapor fractions by fluid in the downcomers. With reference to Fig. 3, it will be apparent that if the vapors were permitted to pass through the downi comer indicated at A associated with the tray B from which fluid representing the lighter ends is removed by withdrawal through the pipe C that the fluid withdrawn from a lower level as through pipe D representing a heavier fraction will carry with it some of the lighter ends or fractions that should have been carried off through the pipe C at the level of the tray B. Assuming that C represents a gasoline fraction whereas D represents a fraction of the nature of kerosene, the recovery at C will have been deficient while the recovery at D will represent a lighter than normal fraction. The baiiles l3 serve to efiectively prevent entrance of the vapors into the downcomer from the adr jacent tray level and therefore prevent the occurrence of premature fractionation. Furthermore, the baiiie, by virtue of its function in excluding vapor from the downcomer, serves to assume a maximum fluid head in the downcomer, thus to promote the efiicient transfer of fluid from one level to the next lower level, a feature which is of particular importancewhen the bubble tower is operated at or near maximum capacity.

With reference particularly to Fig. 2, it will be noted that the wall portion iii of the bubble tray is concave in form, thus to provide a basin within which a pool of fluid is maintained, thereby to seal the outlet of the downcomers against the passage of vapors upwardly therethrough from a lower to a higher tray level, It has been the practice in the past to maintain this pool by the provision of a wall coextensive with the tray assembly that is substantially flat and is usually located in a horizontal plane, a dam being employed to maintain a level sufficiently high to insure the immersion of the lower end of the downco'mers in the fluid. In my improved bubble tray construction I form the concave wall portion i8 contiguous with the weir of the dam so that the portion of the greatest depth of the pool may lie between the dam and the adjacent edge .of the downcomer outlets, the wall being curved gradually from that point to the adjacent tower wall i. This structure and arrangement of parts permits of the sweeping of the wall 88 by the fluid as it is discharged through the downcomer to carry heavy matter which might otherwise accumulate to choke the downcomer outlet over the dam 8 and through across the trays. If the heavier substances are thus maintained in circulation in the fluid system there is little possibility of harmful accumulation. Furthermore, by virtue of the curvature of the wall l8 as described the settling and accumulation of tarry and other heavy substances, if such does occur, will take place at a point to one side of the outlet of the downcomers,

thus obviating the possibility of choke fluid flow and permitting of the subsequent sweeping of the accumulation into the fluid streams at a later that mydisclosure herein is illustrative only and not limitative and that I am to be limited only by the scope of the following claims.

I claim: 4

1. In a bubble tower, a plurality of bubble trays, means for conducting upwardly rising vapors through each tray, inlet and outlet pools on each t ay, 11 downcomer for separately conducting liquid downwardly from the outflow pool on one tray to the inflow pool on the next lower tray without'coming into direct contact with upwardly rising vapors, a dam higher than the inlet to said downcomer separating said outflow pool from the bubble section proper of each tray, for the purpose of maintaining a constant liquid level on said bubble tray and a baflle mounted above and spaced from the inlet of the downcomer and bebubble section, a downcomer for conducting liquid from the outlet pool of each tray to the inlet pool of the next lower tray, the lower end of said downcomer extending belowthe level of the dam separating the said inlet pool, thereby preventing access of vapors to the lower end of said downcomer,

a horizontal imperforate baflle plate mounted above and spaced from the inlet of said downcomer and below the level of the dam separating said outlet pool from said bubble. section, where-- by vapors are prevented access to the upper end of said downcomer and flooding of the tray is prevented when the amount of reflux liquid becomes excessive.

3. The bubble tower construction of claim 2 wherein the contour of the bottom of said inlet pool is curved concavely and continuously to the top of said dam to facilitate the discharge of solid material over said inlet dam and thus prevent restriction of the flow of reflux through said downcomer by said solid-material.

GEORGE W. WATTS. 

